Effect of ball milling



United States Patent Oifice Re. 26,942 Reissued Aug. 25, 1970 26,942COCRYSTALLIZED CATALYST PREPARATION PROCESS Erik Tornqvist, Roselle, andArthur W. Langer, In,

Watchung, N..I., assignors to Esso Research and Engineering Company, acorporation of Delaware No Drawing. Original No. 3,130,003, dated Apr.21, 1964, Ser. No. 19,176, Apr. 1, 1960, which is a continuation ofapplication Ser. No. 532,513, Feb. 16, 1966. Application for reissue May16, 1969, Ser. No. 827,112 Int. Cl. C(llg 23/02 US. Cl. 23--87 13 ClaimsMatter enclosed in heavy brackets appears in the original patent butforms no part of this reissue specification; matter printed in italicsindicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE An olefin polymerization catalyst componentis produced by intensely milling together in the absence of diluent apartially reduced transition metal halide (such as TICI and a group IIor III metal halide (such as AlCl This application is a continuation ofS.N. 532,513, filed Feb. 16, 1966, and now abandoned.

This invention relates to polymerization catalysts and more particularlyto polymerization catalysts useful for the low pressure polymerizationand copolymerization of alpha olefins.

Prior to the present invention, it was found that ethylene and otherolefins such as propylene, butylene, isobutylene and the like can bepolymerized and copolymerized at relatively low pressures notsubstantially exceeding atmospheric pressure in a liquid reaction mediumwhen using various combinations of reducing metals or metal compounds,e.g., alkali and alkaline earth metals, their hydrides and alloys;aluminum compounds, such as aluminum hydrides, aluminum alkyls, e.g.,aluminum trialkyls, alkyl aluminum halides and the like with variousreducible heavy metal compounds, such as the halides, acetyl acetonates, and the like of the metals of groups IV through VI and VIII ofthe periodic table, e.g. of titanium, zirconium, vanadium, chromium,molybdenum and iron. See, e.g., Belgian Patent 533,362; Chemical andEngineering News, April 8, 1957, pages 12 through 16, and PetroleumRefiner," December 1956, pages 191 through 196.

Prior to the present invention, it was also discovered that catalystsystems made up of a preformed partially reduced transition metal halidecocrystallized with a group II or III metal halide is a much more activealpha olefin polymerization catalyst component than the preformedpartially reduced transition metal halide containing no cocrystallizedgroup II or III metal halide. Additionally, it was found that drymilling the cocrystallized catalyst component produces a catalystcomponent which, when activated with an organo metallic compound, is ahighly active catalyst for all alpha olefins, giving very highpolymerization rates and high catalyst etficiencics.

It has now been found that cocrystallization of a preformed partiallyreduced transition metal halide with a group II or III metal halide canbe obtained by intensely milling the preformed partially reducedtransition metal halide with the group II or III metal halide when themilling is carried out in a steel ball mill. The activity of thecocrystallized catalyst component of the invention is much greater thanthat of the correspondnig preformed partially reduced transition metalhalide, which has been steel ball milled alone for an identical periodof time. By contrast, no increase in catalyst activity is obtained whenseparately ball-milled group II or III metal halide is added to andthoroughly mixed with the pure ball milled transition metal halide aslong as the mixing does not involve the intense grinding of thisinvention.

The partially reduced transition metal halides that are dry ball-milledprior to activation with an orguno-metallio compound are the halides,such as the iodides, bromides, and preferably the chlorides, of thetransition metals of the IV-B, V-B, VI-B and VIII groups of the periodicsystem according to Fundamental Chemistry," 2nd Ed., by H. G. Deming,John Wiley & Sons Inc, such as titanium, zirconium, thorium, vanadium,tantalum, molybdenum and tungsten. The term partially reduced transitionmetal halides is to be understood to mean transition metal halides inwhich the transition metal components have a valence at least one unitbelow their normal maxi mum valence. The group II or III metal halidecocrystal lized with the preformed partially reduced transition metalhalide preferably contains the same halogen as the latter. Thus in thecase of a transition metal chloride, the group II or III halide ispreferably a chloride such as aluminum chloride, gallium chloride, orberyllium chloride; with aluminum chloride preferred. Titaniumtrichloride is preferred herein, especially the purple crystallinemodifications TiCl where n is a number between two and three can also beused. The partially reduced transition metal halide is mixed with agroup II or III metal halide in the range of from 0.05 to 1.0,preferably 0.1 to 0.5, and more preferably 0.2 to 0.33 mole of the groupII or III metal halide per mole of partially reduced transition metalhalide.

The partially reduced heavy transition metal halides can be prepared byany procedure known to the art and the preparation of these compounds isnot within the scope of the invention. However, two of the methods knownfor preparing the preferred metal halides, i.e., partially reducedtitanium chlorides are summarized below:

(1) Metal reduction of titanium tetrachloride with titanium powder inthe absence of solvent at elevated temperatures.

(2) Hydrogen reduction of titanium tetrachloride at temperatures aboveabout 650 C.

The milling process of the invention is carried out by placing the drypreformed partially reduced transition metal halide and the group II orIII metal halide in ball milling equipment and milling the metal halidein the absence of diluents in an inert atmosphere, such as nitrogen orargon atmosphere, which is free of oxygen, water vapor, and othercatalyst poisons for a period of time sufficient to cocrystallize thetwo components and substantially increase the activity of the transitionmetal halide in the polymerization reaction when activated with anorgano-metallic compound. It was found, however, that the use of agrinding medium of density greater than 3 g./ml., such as steel balls,was necessary, and that the use of flint pebbles even for periods of 17days did not form the cocrystallized compounds of the invention. Theoptimum time period for the dry milling step depends in general on theefficiency of the equipment used and the particular preformed partiallyreduced transition metal halide used. Ball milling times of from about 2to 20 days were used herein. The time period most suitable for any givenmilling equipment can easily be determined by routine experimentation.

Based on this discovery, one should of course be able to devise grindingequipment which can utilize grinding materials of lower than 3 g./ml.density, e.g., the effective density could be increased by utilizingcentrifugal force or high velocity impact.

It was proved by vacuum sublimation that surprisingly, truecocrystallization of the partially reduced transition metal halide andthe group II or III metal halide takes place under the conditionsdescribed. Further proof of the cocrystallization was given by thehighly increased polymerization rate obtained with the product of thisinvention as compared with a similarly ball milled partially reducedtransition metal halide alone or a simple mixture of the two componentsball milled separately. It was quite surprising, and actually contraryto what normally would be expected, to discover that truecocrystallization of the two components could be obtained by a physicalmethod such as intense ball milling.

The dry milled preformed partially reduced transition metal halidecocrystallized with the group II or III metal halide is removed from themilling equipment at the end of the milling period and activated with anorganometallic compound in an inert diluent. The organometalliccompounds useful in the present invention for activating the dry milledmetal halides are organometallic compounds of the metals of groups I toIII of the periodic system. Particularly valuable are alkyl aluminumcompounds, especially trialkyl aluminum compounds such as triethylaluminum, tripropyl aluminum, triisobutyl aluminum, and the like, anddialkyl aluminum compounds such as diethyl aluminum halides, e.g.,diethyl aluminum chloride, dipropyl aluminum chloride, diisobutylaluminum chloride, and the like. Monoalkyl aluminum halides can also beused. Additionally, organoaluminum compounds having one or twohydrocarbon radicals and two or one electron attracting groups such asalkoxy, organic nitrogen or sulfur groups can also be used. Triethylaluminum is particularly preferred herein.

The dry milled cocrystallized metal halide catalyst component is treatedin a non-oxidizing atmosphere in an inert diluent with one or more ofthe above organo-metallic compounds in a mole ratio of 0.1 to 6 mols oforganometallic compound per mole of dry milled metal halide at atemperature in the range of to 135 C. The temperature is not criticalhere although elevated temperatures which will result in decompositionsof either or both of the components should, of course, not be used.

The inert diluents suitable as a medium for the activation of the drymilled metal halides include aliphatic hydrocarbons such as n-hexane,n-heptane and n-decane and aromatic hydrocarbons such as benzene,toluene, xylene, halogenated hydrocarbons such as chlorobenzene, and thelike, with an aromatic diluent, particularly xylene, being preferred.

The dry milled cocrystallized preformed partially reduced transitionmetal halide component after being activated with an organo-metalliccompound is used to homopolymerize alpha olefins containing two or morecarbon atoms and to copolymerize alpha olefins such as ethylene andpropylene. The homopolymerization of alpha olefins such as for examplepropylene, butene-l, heptene-l, dodecene-l, and the like and thecopolymerization of two or more alpha olefins such as mixtures ofethylene and propylene, ethylene and butene-l, propylene and butene-l,and the like, is carried out by contacting the desired olefin feed withthe activated dry milled metal halide in a hydrocarbon solvent at atemperature of from 0, to about 100 C., preferably 50 to C., and atpressures ranging from sub-atmospheric to 150 p.s.i.g., preferablyatmospheric pressure, in batch or continuous operation. The catalystslurry is preferably diluted with additional diluent to provide acatalyst concentration for the polymerization of about 0.1 to 0.5 wt.percent based on the weight of the diluent present. The polymer productconcentration in the polymerization reaction mixture can range betweenabout 1 to 20 wt. percent based on the total contents present. It shouldbe noted that the polymerization process of this invention allows theuse of more concentrated polymer slurries than are practical in priorart processes. When the desired degree of polymerization has beenobtained, a C to C alkanol such as isopropyl alcohol or n-butyl alcohol,desirably in combination with a chelating agent such as acetyl acetoneor diacetyl, is added to the reaction mixture to dissolve and deactivatethe catalyst and to precipitate the polymer product from solution. Thepolymer product is then filtered and can be further washed with alcoholor an acid such as hydrochloric acid and dried, compacted and packaged.It is important that the polymerization reaction be carried out in theabsence of catalyst poisons such as water, oxygen, sulfur compounds, andthe like. The activated dry milled metal halide catalyst of theinvention can be added to the olefin-saturated diluents atpolymerization temperature without encountering reactor fouling. This issurprising and is of particular importance in continuous polymerizationreactions where a direct addition of catalyst to the reactor atpolymerization temperatures is highly advantageous.

The invention will be better understood from the following examples.

EXAMPLE I 308.6 grams (2 moles) of a TiCl catalyst component which hadbeen prepared by the reduction of TiCl, with hydrogen at about 700 C.was ball-milled for seven days with chrome alloy steel balls in a /2gallon jar with 26.7 grams (0.2 mole) of AlCl (anhydrous). At the end ofseven days, the product was recovered from the ball mill, 0.42 gram ofthe product was added to ml. of xylene in an addition funnel andactivated with 0.54 gram of AlEt After about 15 minutes the catalystslurry was added to a glass polymerization unit containing 900 ml.xylene satuarted wtih propylene at 60 C. and equipped with a stirrer anda dip tube for continuous introduction of monomer. The temperature wasbrought to 75 C. within 10 minutes and the polymerization continued atthis temperature for an additional 50 minutes under continued monomeraddition and good stirring. After one hour of total polymerization time,the reaction was terminated and the polymer precipitated by the additionof 2 volumes of isopropanol containing 3 ml. of acetylacetone, and theprecipitated polymer filtered. The filtered polymer was given a secondisopropanol wash, filtered again and dried in a vacuum oven. The detailsof the catalyst preparation, the polymerization reaction, and thepolymer yield and properties are given in Table I together with datafrom a similarly ball milled sample of TiCl which had been milled in theabsence of aluminum chloride.

Table I EFFECT OF BALL MILLING TiCh WIIH AlCla N ACTIVITY IN ATMOSPHERICPRES- SURE PROPYLENE POLYMERIZATIONS Example Catalyst I II III IV VTiCli.nAlCls, Composition- TlCla TlC1a.0.1 TlCls.0.2 'IlCh.0.33TiCh.0.5A1Cl: 'IiCla. AlCl:

AlClz A101: A101:

Ball Milling Time, Days Weight, g 0. 386 0.4 0. 453 0. 500 0. 553 0. 5530. 718 AlEts, g 0. 57 0. 54 0.51 0. 475 0. 428 0. 570 0. 855 AllIi Ratio2 2 2 2 2. 3 Catalyst Concentration,

0. 96 0. 96 0.96 0.98 0. 98 1.12 l. 57 Polymerization Result id, g 52.895. 8 132.0 131.8 47.9 74.4 21. 5 Waxy Polymer, Percent 0. 5. 0 5.4 3.64. 4 3.9 6. 1 Catalyst Efllciency,

g./g 55. 5 102.9 137.0 135.3 .9 66.3 13.7 Properties of Solid Polymar:Molecular WeightxltH 18 210 215 1 16 205 185 Density, g [ml 0. 9002 0.8993 0.8993 0. 8976 0.8926 0.8969 0.8956 (1--.. 168 I61 160 I I62 I62Tensile Strength, p.s.l 4,780 4,410 4,380 4,390 3,910 Elongation,Percent 160 150 400 50 110 Ash, Percent 0. 024 0. 008 0.022 0. 009 0.057 0.013

( Includes A101: in 'IlCl:.nAlCh reparations. According to the Harrisoorrelat on, J. Polymer Science, 8,360 (1952).

EXAMPLES II THROUGH V EXAMPLE VII TiCl .nAlCl catalyst components wereprepared and tested according to the process of Example I. The value ofn for Examples II through V varied from 0.2 to 1 as shown in Table I.The details of the catalyst preparation and the use of the catalyst topolymerize propylene are also given in Table I.

It can be seen from above Table I that the cocrystallized catalysts ofExamples I through IV had higher catalyst efficiencies and smallerquantities of waxy polymer than that of TiCl steel ball-milled in theabsence of aluminum chloride. Surprisingly, this increased catalystefliciency was obtained at essentially no sacrifice of polymerproperties. Example V, which exhibited a much lower catalyst eificiencythan any of the other examples, shows that the ratio of aluminumchloride to TiCl should be kept below 1 when the degree of grinding isequal to or lower than that employed in Examples I-V.

EXAMPLE VI In order to demonstrate the applicability of the process ofthe invention with systems other than titanium halides, 157.2 grams (1mole) of VCl were steel ball milled in a quart jar with 44.4 grams /3mole) of AlCl in accordance with the process of Example I. Details ofthe catalyst preparation and the polymerization of propylene using thecatalyst are given in Table II together with a sample of VCl ball milledfor seven days in the absence of AlCl for comparison purposes.

Table II ATMOSPHERIC PRESSURE PROPYLENE POLYMERIZA 1.543 grams (10moles) of TiCl and 133.3 grams (1 mole) of AlCl were milled together ina 2% gallons flint pebble mill for seventeen days. However, no improvement in catalyst activity was obtained compared to that of a sampleof TiCl which had been flint pebble milled alone under the sameconditions for 18 days.

This example demonstrates that flint pebble mills are not satisfactoryfor making the cocrystallized catalyst components of the invention.

EXAMPLE VIII A TiCl AlCl catalyst was prepared by mixing calculatedamounts of TiCl and AlCl which had been steel ball milled separately forsix days. A 0.5 gram aliquot of the mixture was then used forpolymerization of propylene exactly as described in Example Ill. Thecatalyst activity proved to be lower than for the pure steel ball milledTiCl tested under corresponding conditions (Table I), i.e., 38.2 vs.55.5 g./g. This further demonstrates the importance of intenselygrinding the two solid components together.

In order to demonstrate that the cocrystallized catalyst components ofthe invention are not simply mixtures of partially reduced transitionmetal halide and group II or III metal halide, vacuum sublimation wasapplied to the ball milled TiCl -0.33 AlCl mixture tested in Example IIIand a similar mixture of TiCl and AlCl which had been prepared byshaking for three days. With the mixture formed by shaking, essentiallyall of the AlCl was lost by vacuum sublimation at 5 mm. of mercury for 4hours at C., while essentially none of the AlCl was lost from the steelball mixed sample.

Variations in the process of the invention can be carried out withoutdeparting from the scope or spirit of the invention. Additionally theexamples have been given for illustration purposes only and are notmeant to limit the invention.

What is claimed is:

1. The process for the preparation of a catalyst component useful in thepolymerization of alpha olefins comprising intensely milling together inthe absence of diluent and with a grinding medium having an effectivedensity higher than 3 g./ml., a mixture which consists essentially of apartially reduced transition metal halide of the transition metals ofgroups IV-B, V-B, VI-B, and VIII of the periodic system and a metalhalide of a metal of groups II or III of the periodic system; from 0.05to 1.0 mole of the metal halide of groups II and III being employed permole of partially reduced transition metal halide.

2. The process of claim 1 wherein steel balls were employed as thegrinding medium.

3. The process of claim 1 wherein the intense ball milling is carriedout for from 2 to 20 days.

4. The process of claim 1 wherein the partially reduced transition metalhalide is a titanium halide and the metal halide of groups II and III isan aluminum halide.

5. The process of claim 1 wherein the partially redueed transition metalhalide is a titaninum chloride and the metal halide of groups 11 and Illis aluminum chloride.

6. The process of claim 1 wherein from 0.1 to 0.5 mole of metal halideare employed per mole of partially reduced transition metal halide.

7. The process of claim 1 wherein the transition metal halide is avanadium halide and the metal halide in groups II and III is an aluminumhalide.

8. The process of claim I wherein the partially reduced transition metalhalide is a vanadium chloride and the metal halide of groups 11 and IIIis aluminum chloride.

9. Method of preparing TiCl for use in combination with a cocatalystselected from the group consisting of aluminum alkyls and aluminum alkylhalides in the low pressure polymerization of olefins which consistsessentially in grinding a mechanical mixture of TiCl and an ReferencesCited The following references, cited by the Examiner, are of record inthe patented file of this patent or the original patent.

UNITED STATES PATENTS 2,893,984 8/1959 Seelbach et al. 2,956,989 10/1960Jezl. 3,032,510 5/1962 Tornqvist et al. 3,069,364 12/ 1962 DAlelio.

FOREIGN PATENTS 1,132,506 11/1956 France.

PATRICK P. GARVIN, Primary Examiner U.S. Cl. X.R.

